Process for the noncatalytic cracking of a hydrocarbon oil



Feb. 1, 1949. J, w, oy 2,460,463

1 Rooms FOR THE NONCATALYTIC CRACKING OF A HYDROCARBON OIL Filed Nov. 7', 1946 CRACKED VAPORS T0 RECOVERY SYSTEM l6 I7 2 I 20 2 I. 'J

CHARGE.

FROM l9 HEATER as 2o 2o I FIG. 2 I I I LIQUID I RESIDUUM /NVEN7'OR V J. w. LOY

ATTORNEYS Patented Feb. 1, 1949 PROCESS FOR THE NONCATALYTIC CRACK- I ING OF A HYDROCARBON oin John w; Loy, Bartlesville, kla., assignor to Philv lips Petroleum Delaware Company, I a corporation of 7 Application November 7, 1946; Serial No. 708,246

3 c ims. (01.; 196-160) This invention relates to W, the noncatalytic cracking of hydrocarbon oils. In one of its more specific aspects it relates to a reaction chamber of improved design in which to carry out mixed phase crackinggof relatively heavy or high boiling petroleum fractions for the production of gasoline of improved quality and yield.

Processes for cracking of petroleum, or hydrocarbon fractions have been'divided into two types, catalytic and noncatalytic. The latter type is frequently called thermal cracking, but this terminology should not be so limited in the strictest sense of the word since both methods involve super-atmospheric temperatures. However, the use of the term thermal cracking as applied to noncatalytic cracking is a very convenient and frequently used term, and will be used herein to mean noncatalytic cracking.

In the thermal cracking plocessthe oil to be cracked may be heated in a tube or pipe heater and then at substantially reaction temperature discharged into a vessel generally termed a --reaction chamber. Reaction chambers frequently are merely cylindrical shaped steel vessels set on end, and of course are well insulated against loss of heat. The hot oil charge enters the chamber through the sidewall at apoint near the top. Vapors leave through anoverhead vapor line while botoms leave through a bottom draw pipe.

One advantage of a reaction chamber as compared to coil cracking for heavy or residual oils is that the relatively nonvaporizable residuum may be removed from the bottom of the chamber after ashort residence time at cracking conditions, whereas the remainder of the charge to the V up of a coke layer on the walls of the cracking tubes unless a very dense phase is maintained through high pressure. And further, high pressures sometimes unfavorably influence cracking products and their yields;

Reaction chamber cracking has many advantages for the cracking of heavy oils and these are well known in the cracking art. 7 m

In recent years there has been a general improvement in the octane number ofgasoline marketed, to the consumer, nation wide,

and where a refiner does not have catalytic cracking facilities, or where the oil to be cracked cannot readily be handledcatalytically, existing reaction chamber equipment is found to be deficient in giving the quality of gasoline desired, concomitant with operable treatment of residuum product of the cracking process.

There is a limit to the flexibility and adequacy of the conventional reaction chamber for cracking the vaporizabl constituents without coking the residuum. I

This obstacle can be overcome, I have dis covered, by a rather simple and inexpensive improvement over existing equipment which involves installation of an inverted Vessel (lower end open) within a. conventional reaction chamber.-

Clneobject of my invention is to provide an apparatus through the use of which thermal crack- .ing of hydrocarbons is improved.

Another object of my invention is to provide a simple and inexpensive apparatus for use in conjunction with existing thermal cracking reaction chambers whereby the thermal cracking operation is improved with the resulting production of better quality gasoline.

Still another object of my invention is to proparent from a study of the following disclosure and attached drawing which respectively describes and illustrates the apparatus of my in vention.

Figure l of the drawing illustrates one embodiment of my secondary chamber as installed within a thermal cracking reaction chamber.

Figure 2 is a horizontal section of the vessel taken on the line 2--2 of Figure 1. r

' Referring to the drawing, a vertically disposed cylindrical shaped reaction chamber II is fitted in its upper end with an overhead vapor line l2 which conducts vapors from the vessel to a subsequent process step. The bottom of the vessel is fitted with a bottoms draw-off line l3 through which bottoms or residuum passes to subsequent process steps or to cooling and storage. The vapor line 12 has a valve 4 for control of vapor flow while liquid flow through the bottoms line 13 is controlled by a valve I5.

1 V A pipe 16 enters the chamber at about amid point,- as shown in the drawing. 'A valve H in this pipe controlsfiow of materials therethrough.

This pipe l6 passes through the wall of the vessel II at an angle so that the inner end of the pipe may terminate in the cylindrical wall of an inner cylindrical vessel is as an"oval shaped opening [9. 'Fluid from pipe I6 is intended to enter the inner vessel i8 tangentially to the inner wall thereof and'substantially normal-to the l on? gitudinal axe's -of *both" vessels H and I8. The longitudinal axes of said vessels II and I8 substantially coincide.

In conventional thermal cracking reaction.

chambers the fluid inlet line eerr spqi e ng toline It enters the vessel at a point somewhat near the top, and not necessarily at an-anglje-tothe vessel wall. The line usually enters the upper portion of the vessel at right anglesto the vessel wall and terminates at the wall, that is,', -,does not extend to a point within the volume of the vessel.

The inner vessel i8 is'cylindrical in shape' 'tvith" closed top and an open bottom as illustrated in Figure l. Vessel t8 is-dis'pose'd a spaced'dis't'an'cfe from the ends of the outer chamber but is pref erablycloser to the bottom than the top of the: outer chamber. Thereis no fixed relationship between the main chamber "and the secondary chamber since the proportional size'of' thetwo will depend upon individual requirements. The cross sectional area of the inner chamber should, however, be less than thecrosssectional area of the annular space between the two cl'i'ambers',

as is indicated in Figures 1 and 2.; Tangential entry of the charge to the secondary' cha'mb'r is preferred. The newdesign is adaptable to the commonly used two-coil operation w'herei'n' a relatively heavy fraction is preheated. in one coil and lighter fraction is preheated'tofahigher reaction chamber i l'. Sufficient pressureis'held upstream of this-valve so that excessive crack? ing and/or vaporization will not'focour f 011' at cracking temperature passes-through A valve ll is in line it ar a 4 the ratio of the respective residence times at cracking temperature of the liquid and vapor phases is much reduced.

Vapors formed by vaporization and by cracking' of liquid and vaporous hydrocarbon pass downward within this inner chamber, then change tlirecti'on Ito fi wqimwarafin the annular space between" the chambenlfi and the walls of the main reaction chamber Ii. By so doing, all or substantially all liquid or mist is removed from the vapors and the vaporous material leaving-"the reaction chamber by the overhead line 12 is free from residual or tarry material. This operation maybe'contrasted with conventional operation'in'whiohthe transfer line discharges its mixed vaporous, liquid and tarry material into the top of thegchamber and the liquid and tarry is carried out either on overhead or bottom line to a dephlegmation and subsequent fractionation steps. In fother words there is less or'suhstantially'no-liquid or'tar entrainment in the "overhead vapors leaving my reaction chamber I I. The secondary chamber should not be'so oloseto the bottom of the primary chamber thatdropi'gf liquid or mistcannotbe separated therefrom.

Due to the rapid'rate of travel of liduidaround:

the'walls of "the'inner vessel 48, there may be little deposition ofc'oke. The tar rapidly-falls or drains" to the bottom of the chamber If and is withdrawn through pipe 23 as controlled'by valve 15. Little or no liquidlevel is maintained inf'the vessel l {for-even some little vapor-may be withdrawn-throughthe tar draw t3 to assist the'transfer line it -a'nd'thr o'ughthe: pressure reducingvalve i? to enter the inner vessel?near its top, through the opening l9. The-oil enters this vessel at a rather high velocity since-on passage'through the valve l i considerable f xation ization occurs, and further, the heated oil travels through the transfer line at a rather rapid rate. The oil then enters the vessel 3, at a pointbn its inner periphery and due to its velocitytravels around the innerwalls. The efiect "oifgr avity gradually oauses'the oil to pass downward {and finally to: drop from the walls of the inner ve to the" bottom of the outer vessel H. the oil which is flowing around the walls'of" inner-vessel travels substantially in a h c path. Due to the relatively'great centrifual" force'acting on this rapidly traveling ioillthe great difference in density between newly formed valpors and the residual oil, and the relativelysma-ll diameter of the internal vessel, separation-be" tween the oil and vapor is much 'morerapidth an I mdvalof any coke -fr'o'mithe *chamberbottom;

when the oil to be cracked enters a rea' otion cham berin the conventional manner. In other-words:

' in theniore rapid"withdrawal of the' bottoms.

Speedy withdrawal of these high temperature bottoms shortens, of course, their residence time in the chamber at reaction temperature and ac cordingly assists in'minimizing cokeimfin'ation therei'nfl- 7 H I a v lfifi'thdrawal offtoo 'm'uch' vapor with the botterns tends'to' prevent'normal vapor how'through theoverheadwapor line; the vapo'r withiz'i'the' chamber'tends to become overcracked, and more" extensive dephlegmating equipment is required be elevated considerably over'what would be'p'os siblewith the old design (or the depth of cracking otherwise increasedl-and this will effect: an important increase in the degree of cracking of the vaporphase with a corresponding increase in the-Quality Of ga'SOllhe yielded from theproessi without coking the" residuum product or other wise? impairing its characteristics as regards its dl'sfis i'tion'; in co mercial file! oil lnalke'ts. I

By theluse'ofthe inrier vessel l8 es -herein dis; closed the-residen'e-time of the vapor phase within'thecharnberis about the same as if 'tl ie'inner vessei were not used, but the residence time of the] residual liquid and tarry material isfsho'rtene'd, so t-hat due to the formation oflesscolie witlii-"nthe chamber longer onstream periods" support members for the inriervessel i8 ma' -be of: any. type or kind desired and found slli tablefor'the purpose at h and. it is usually better to support" this inner vessel from its top than from the bottom, since no support members are then present to interfere with eventual'reqgirurp se l ra n. se esi ori me bers are shown as attaching'the inner've s'sel to thereac'tiorr chamber;

Materials of construction for the main reaction chamber may be selected from among those ordinarily used while the inner vessel [8 may preferably be made from relatively lightand inexpensive steel plate and rigidly supported. The outer chamber is of course well insulated against loss of heat.

It will be obvious that the relative size of the secondary chamber l8 may be varied, and its position altered with respect to the bottom of the 7 primary chamber l I, as individual or specific conditions warrant.

Having disclosed my invention, I claim:

1. An improved method for noncatalytically cracking hydrocarbon oil which comprises in combination the steps of heating said oil to its separation zone and into the upper portion of said.

enlarged reaction zone; maintaining said vapors in said reaction zone for more complete cracking; and removing effluent vapors from the upper por tion of said reaction zone.

2. An improved method of noncatalytically cracking hydrocarbon oil which comprises in combination the steps of heating said oil to its cracking temperature; reducing the pressure on said oil; introducing said oil, at a relatively high velocity, tangentially into a cylindrical separation zone at a point adjacent its top, which zone is unobstructed except for being closed at its top; rapidly separating vapors and residual liquid in said separation zone by centrifugal force; passing said separated products downwardly from said separation zone into an enlarged reaction zone surrounding and extending beyond each end of said separation zone; removing residual liquid and a small portion of vapors from the bottom of said reaction zone; passing the remaining portion of vapors upwardly, at a, relatively low velocity, around said separation zone and into the upper portion of said enlarged reaction zone; maintaining said vapors in said reaction zone for more complete cracking; and removing efiiuent vapors from the upper portion of said reaction zone.

3. An improved method for noncatalytically cracking hydrocarbon oil which comprises in combination the steps of heating said oil to its cracking temperature; reducing the pressure on said'oil; introducing said oil tangentially and at a relatively high velocity into a cylindrical separation zone which is closed at its top; rapidly separating vapors and residual liquid in said separation zone by centrifugal force; passing said separated products downwardly from said separation zone into an enlarged reaction zone surrounding and extending beyond each end of said separation zone; removing residual liquid from the bottom of said reaction zone; passing said vapors upwardly, at a relatively low velocity, around said separation zone and into the upper portion of said enlarged reaction zone; and removing eiiluent vapors fromthe upper portion of said reaction zone.

JOHN W. LOY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,455,376 Adams May 15, 1923 1,824,215. Kirschbraun Sept. 22, 1931 2,125,921 Hillhouse Aug. 9, 1938 2,289,329 Prickett, July 7, 1942 2,413,407 Dreyfus Dec. 31, 1946 2,416,404 Proell Feb. 25, 1947 

